From there on, Mullan thought he only had one or two years left, but now he's not so sure.
He has been an unwavering supporter of voluntary euthanasia for most of his life.
"My interest in this whole debate is about choice.
"And I suppose what troubles me a little bit is that people on the other side are already getting their choice. They don't want it, it's not going to happen, they're fine they've got that choice.
"But there's a small minority of us on the other side who may find ourselves in extreme pain that cannot be treated and we may want to make the choice that this is enough."
Mullan says he was pleased to watch the End of Life Choice Bill pass its first reading in Parliament on Wednesday night.
He says if the bill passed into law, and he met the criteria, he might use it.
"The cancer is in my spine.. In my lower spine, so the probability of when the drug loses hold and the cancer gains control again, I'll progressively become paralysed. And I don't want to be in that kind of situation for the last days and weeks of my life when there would be an alternative possibility."
Mullan says he's surprised that New Zealand is going to be so far behind Victoria, Australia, which legalised voluntary euthanasia in October.
He says the next nine months are critical.
"If this committee has to deal with the 22,000 submissions that went to the last committee, they won't have a prayer of getting through it all in nine months... and it could drag out for a long time."
Mullan says he's really disappointed about the proposed referendum that was agreed to under the Labour-led government, saying it will slow the process down by another three years.
"That will highly likely make it impossible for me. And I guess I would've liked to have seen a bill in place that I might have been able to use if I needed it. The chances are now is it's not going to be.
"And I'm disappointed about that, personally. For the whole country, it just means that a few dozen people, like me, will just have to wait a little bit longer or miss out."
"What it also means is that people in my kind of situation, and they found this in Victoria and they gave the numbers of people in my situation, who committed suicide ...because they could see that the time was going to come and they weren't going to be able to do it. And the evidence is that all of those people died younger than they needed to."
He disagrees with those against voluntary euthanasia, that people are going to be coerced into doing something they don't want to do.
"That hasn't been the experience in countries where there is a good regulatory framework in place for this.
"And David Seymour's bill is pretty good in that regard. People are not reading the fine print."
